The present invention relates to a filter and an X-ray imaging apparatus, and more particularly to a filter that adjusts energy spectra of X-ray, and an X-ray imaging apparatus provided with the filter.
An X-ray imaging apparatus irradiates X-ray to a subject by adjusting energy spectra of the X-ray with a filter. The filter is provided in a collimator box attached to an X-ray tube. In order to obtain desired spectra, the filter can be used by switching plural filter plates attached to a rotating disc (e.g., see patent document 1).
[Patent Document 1] Japanese Published Unexamined Patent Application No. HEI11-76219 (p. 2, FIG. 1)
Spectra can desirably be adjusted in a wide range with close attention, but in the construction in which the filter plates are switched by the rotating disc, a four-step adjustment is about all this construction can provide. Therefore, widening the adjustment range causes a rough step, while providing more steps narrows the adjustment range. When a multi-step adjustment is made possible in the rotating disc system anyway, the rotating disc to which a great number of filters are attached is increased in size, thus unrealistic.